Investigation of bed-to-wall heat transfer characteristics in a rolling circulating fluidized bed

• Particle volume fraction in clusters is higher in rolling CFB.
• Thickness of gas layer between clusters and wall decreases in rolling CFB.
• Predicted heat transfer coefficients by ICBM I agree well with experiment results.
• Rolling period presents little influence on heat transfer coefficient.

In order to enhance the heat recovery properties of the circulating fluidized bed (CFB) which is proposed to be a potential choice for the waste heat recovery system in a ship to solve the corrosion problem, effect of the rolling motion induced by the ship on the bed-to-wall heat transfer characteristics has been investigated. Improved cluster-based models (ICBM), in which the potential dynamic feature change of clusters induced by the rolling motion is considered, have been proposed for the prediction of the heat transfer coefficient in the rolling CFB. The predicted heat transfer coefficients by ICBM were compared with the predicted results of cluster renewal model (CRM) which is applied commonly to the CFB at upright attitude, and evaluated by the measurement results in the heat transfer experiment. As results, the predicted heat transfer coefficient by CRM agrees well with the experimental results in the CFB at upright attitude. However, in the case that the rolling motion is applied, the heat transfer coefficient is extremely under-estimated by CRM. Meanwhile, the predicted heat transfer coefficient by ICBM I, which takes into account the disappearance of the gas layer next to the wall and the increase of the particle volume fraction in clusters due to the rolling motion, is in good accord with the measured heat transfer coefficient in the heat transfer experiments. The dynamic feature changes of the cluster are proposed to be the primary factors for the heat transfer augmentation in the rolling CFB.

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